Dynamical superfluid and Bose-insulator phases in quantized microcavity lattices

Microcavity exciton-polaritons have emerged as an excellent platform for realizing quantum phases of matter, owing to their ability to undergo non-equilibrium Bose-Einstein condensation. Here, we show that the interplay between multiple quantized levels in microcavities and polariton nonlinearity drives the emergence of unconventional phases. Specifically, we demonstrate that intra-site quantization in microcavity polariton lattices—manifested as multiple energy levels in strongly confined sites—provides a route to manipulating these phases. We show that nonlinear interactions transfer population into excited onsite energy levels, acting as an intrinsic dynamical channel that controls coherence across the lattice. While weak nonlinearity confines polaritons to the lowest mode, yielding a robust superfluid phase with broken U(1) symmetry, strong nonlinearity induces phase diffusion through inter-level mixing. This dynamically generated fluctuation suppresses global phase coherence and drives the system into a dynamical Bose-insulating phase. Transitions between these phases occur either as a non-equilibrium phase transition or a sharp crossover. This study investigates the destruction of global order in a non-equilibrium condensate within a lattice featuring onsite quantized energy levels. Long-range fluctuations suppress superfluid stiffness and the condensate fraction, while persistent local order reveals a dynamical Bose-insulating state.